Polyarylimidazolidines with phenolic hydroxyl end groups

ABSTRACT

Polyarylimidazolidines with a degree of polymerization of about one to twenty and having phenolic hydroxyl end groups and a novel three-step process for their preparation are described. In the first step of the process, an excess of hydrogen cyanide is reactive with an aryl diisocyanate. The excess hydrogen cyanide promotes polymerization and avoids the reaction of the imino hydrogen on the heterocyclic range with the diisocyanate to form cross linkage and associated gel formation. In the second step, a stoichiometric amount of diisocyanate is added to react with the excess hydrogen cyanide and one hydroxyl of a phenolic dihydroxyl end capping group. In the final third step, the dihydroxyl end capping group is added and the remaining diisocyanate reacts with one of the two phenolic hydroxyls on the end capping group.

This is a continuation-in-part of our prior, copending application Ser.No. 07/475,112 filed Feb. 4, 1991 U.S. Pat. No. 5,097,010 which is acontinuation-in-part of our prior copending application Ser. No.07/475,112 filed Feb. 5, 1990 now abandoned both of which areincorporated by reference as if rewritten herein.

FIELD OF THE INVENTION

This invention relates generally to polymer compositions that are foundby reacting isocyanate and labile-hydrogen functionality. Moreparticular the invention relates to thermally reversible polymercompositions that are capable of thermally dissociating into thereactant isocyanate and labile hydrogen. Such thermally-reversibleisocyanate-based polymer compositions are useful, among other things, ascoatings, hot-melt adhesives, moldings, in reaction injection moldingapplications and in composite or laminate fabrication.

BACKGROUND OF THE INVENTION

Organic polyisocyanates have been used as lacquers, films, coatings andhot-melt adhesives. Since isocyanate compounds are very reactive towardgroups with an active hydrogen such as hydroxyl, carboxyl, amine and thelike, it is common to control such reactivity by adding a monoblockingor masking agent to the isocyanate (U.S. Pat. No. 3,115,479 toWindermuth et al.) and then reacting the blocked isocyanate with apolyester containing free hydroxyl groups by heating the mixture todeblock the isocyanate.

As seen in U.S. Pat. No. 2,777,881, it is possible to avoid the use ofblocking agents by limiting the amount of isocyanate reacted withterminal labile hydrogen groups of a polyester or polyesteramide so asto afford a material that is in an uncured state. Additional isocyanategroups then are added to the uncured product so that a subsequentirreversible cross-linking reaction with moisture can take place toproduce the final cured state with appropriate physical properties.

Another solution that avoids premature introduction of moisture into theproduct is to use a packaging system to protect the isocyanate frommoisture prior to use. Adhesives Age, September 1987, p. 42-43.

U.S. Pat. No. 4,166,873 to Gilliam et al discloses improved hot meltadhesives and coatings formed by adding diisocyanate to polyesters. Theinventors note that the incorporation of isocyanate into the polyestermolecules does not involve chain-extension or significant crosslinking.U.S. Pat. No. 2,982,754 to Sheffer et al. and U.S. Pat. No. 2,876,725 toBuck at al. (example 4) contain additional examples of polyestersmodified by the addition of isocyanates.

U.S. Pat. No. 3,503,927 to Chang et al pertains to a crosslinked networkstructure where the cross-linking is labile to heat and provided by thereaction between a phenolic group and an isocyanate group. U.S. Pat. No.3,684,769 to Abbott et al. pertains to thermally reversible polyester orpolyether urethane polymers with thermally reversible urethane linksbetween polymer chains. U.S. Pat. No. 4,201,853 to Henry et al reveals athermally-reversible polymeric binder for plastic bonded explosives thatreversibly dissociated below 150° C. Wagener and Muria, PolymerPreprints, Vol. 30, No. 1, April 1989 disclose monomeric thermallyreversible urethanes whose molecular weight is a function oftemperature. Although a polyurethane was prepared, no discussion or dataon polymer urethane bond reversibility are given nor are suggestionsmade as to its applicability.

U.S. Pat. No. 4,608,418 to Czerwinski et al. illustrates an attempt toimprove the performance of conventional isocyanate materials by adding areactive plasticizer to a hot-melt composition formed from a mixture ofone or more polyisocyanates and one or more hydroxyl terminated polyolsand one or more chain extenders.

Prior-art isocyanate-based polymers have been low molecular weightisocyanate compositions that afford good working properties, e.g.,application ease, surface wettability and penetration, leveling ability,and gap-filling capacity. Such materials are commonly moisture-cured toform substituted polyureas after being applied to give durable coatingor adhesive materials. However, such materials do not have the highperformance characteristics of some of the more costly high-performancepolymers such as the polyimides. Typically as one attempts to improvethe performance characteristics of the isocyanate-based materials usingconventional techniques, hi9h-viscosity and associated low wettabilityresult in a loss of substrate bonding ability. Currently conventionalisocyanate polymers do not allow for the high temperature processing,e.g., soldering and thermoforming, of flexible circuit boards and othercomponents such as chips, transformers and motors. Conventionalisocyanate polymers typically do not provide cracking resistance at highend-use operating temperatures such as found in high performanceaircraft, automotive and computer equipment. The processibility of highperformance materials such as polyimides that are used in highperformance protective dielectric film or coating materials is morelimited than desired. A need continues to exist for a better,meltprocessible, high- performance material such as a polyimide formolding applications.

SUMMARY OF THE INVENTION

This invention meets these needs and solves many of these problems bypreparing thermally-reversible polymer compositions that containisocyanate-labile-hydrogen based linkages in the polymer backbone and,if necessary, a controlled number of similar crosslinking groups. Theseisocyanate-labile hydrogen based linkages provide cured, crosslinked,three-dimensional polymer networks that are insoluble, strong solids, atroom temperature, but which become soluble, free-flowing melts atelevated temperatures. The polymers become soluble and fusible due to athermally reversible dissociation of the isocyanate-labile hydrogenbased linkage to the isocyanate and labile-hydrogen starting groups atan elevated temperature.

The isocyanate-labile hydrogen based linkage is a urethane linkage whenisocyanate functionality reacts with a terminal hydroxyl functionality.A substituted urea linkage is formed when the labile hydrogenfunctionality is a terminal amine functionality. Other labile-hydrogenfunctionalities form an isocyanate adduct of the functionality.Labile-hydrogen functionalities include, but are not limited to, amides,alcohols (including phenols), amines, oximes, triazoles, imidazoles,imidazolines and iminodiazolidinediones.

Generally both aromatic and aliphatic isocyanate and labile-hydrogenfunctionality form urethane or other bonds that are reversible at someelevated temperature. Typically this temperature is significantly higherfor the aliphatic product than for the aromatic product. Intermediatereversing temperatures can be achieved by using a mixed aliphatic andaromatic product. When high performance polymers are desired, anisocyanate containing a polyarylimidazolidine oligomer includingpoly(parabanic acid) may be used. Often it is desirable to block theisocyanate functionality prior to its reaction with the labile hydrogenfunctionality so as to prevent unwanted irreversible reactions withmoisture and other reactive hydrogen contaminants. As a result, improvedhandling and stability of the isocyanate functionality is obtained. Byusing a volatile blocking agent such as phenol, the blocked isocyanatecan be reacted with the labile hydrogen functionality by heating the tworeactants so as unblock the isocyanate by vaporizing the phenol leavingthe unblocked isocyanate to react with the labile hydrogenfunctionality.

By controlling the stoichiometry of the reactant labile-hydrogenfunctionality and the isocyanate functionality, it is possible to obtaina polymer with isocyanate end groups. By using a nonvolatile blockinggroup in the correct stoichiometry, it is possible to control thereactivity and characteristics of the final polymer product. Providedthere are no interfering reactions with the nonvolatile blocking group,it may be added at any stage of the reaction sequence.

Various characteristics may be incorporated into the polymer compositionby using oligomers with specific properties. For example, aromaticpolycarbonates may be used to provide inherent toughness and impactresistance. By controlling the degree of polymerization of an aromaticpolyester oligomer, a melt liquid crystal property can be obtained. Sucha liquid crystal property provides solid state anchoring or "virtualcrosslinks" so as to minimize the number of actual three dimensionalcovalent crosslinks that need to be used. Polyimides are used to providehigh melting and liquid crystal features. Polyphenylenesulfides haveexceptional strength and rigid, heat stable polymer chains that provideimproved hardness, toughness, and solvent resistance to the polymercomposition. Although hydroxyl end groups are preferably used as theactive or labile-hydrogen end groups, other end groups such as amines,oximes, triazoles, imidazoles and imidazolines may also be used. Toprovide ambient or low temperature flexibility and toughness, flexiblealiphatic polyester, polyether or polycarbonate prepolymers can beincluded in the polymer composition. For example, polyesters formed fromadipic or sebacic acid, dimmer acids, α,ω-butane, pentane or hexanediols, hydrogenated (saturated) phthalic acids, other simple diols andpolyglycols such as polypropylene glycols can be used.

Melt reversibility is enhanced by incorporating ionic functionality intothe polymer composition that is capable of forming thermally-reversibleionic bonds. Typically such thermally-reversible ionic functionality canbe achieved by using a functionality such as an aliphatic carboxylate,sulfonate, or phosphonate that is capable of forming ionic bonds withpreferably a multivalent cation such as zinc, magnesium, calcium ornickel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) show the liquid crystalline region of thebis-hydroquinone ester of isophthalic acid (Example A) at 211° C. Planepolarized optical micrographs (400×) obtained with mettler FP2 hot stageand olympus BH microscope with 40× ULWD (ultralong working distance)lens.

FIGS. 2(a) and 2(b) show the liquid crystalline region of thephenolic-hydroxyl terminated biphenylene sulfide oligomer (Example E) at˜200 ° C. Plane polarized optical micrographs (400×) obtained withmettler FP2 hot stage and olympus BH microscope with 40× ULWD (ultralongworking distance) lens.

In describing the preferred embodiment of the invention which isillustrated in the drawings, specific terminology is resorted to for thesake of clarity. However, it is not intended that the invention belimited to the specific terms so selected and it is to be understoodthat each specific term includes all technical equivalents that operatein a similar manner to accomplish a similar purpose.

Although a preferred embodiment of the invention has been hereindescribed, it is understood that various changes and modifications inthe illustrated and described structure can be affected withoutdeparture from the basic principles that underlie the invention. Changesand modifications of this type are therefore deemed to be circumscribedby the spirit and scope of the invention, except as the same may benecessarily modified by the appended claims or reasonable equivalentsthereof.

DETAILED DESCRIPTION OF THE INVENTION AND BEST MODE FOR CARRYING OUT THEPREFERRED EMBODIMENT

The benefits and potential benefits of the thermally-reversible polymercomposition arise from the basic property of this invention, that is,the ability of the polymer composition to thermally dissociate into itsreactant isocyanate and labile-hydrogen functionalities. This basicproperty allows the composition to flow at a comparatively lowtemperature while exhibiting high strength, good surface adhesion, lowtemperature flexibility, relatively fast development of strength,relatively good solvent resistance, good tear resistance, good impactresistance, and high abrasion resistance.

Generally the formation of the compositions of this invention requiresreacting high performance oligomers possessing appropriate reactive endgroups, i.e., isocyanate and labile-hydrogen functionality capable offorming a isocyanate-labile hydrogen based linkage that is capable ofthermal dissociation into the starting materials. Essentiallystoichiometric amounts of isocyanate and labile-hydrogen functionalityare used.

Two types of structures are prepared. One consists of linearisocyanate-labile hydrogen based linkage in which no trifunctionalisocyanates (or labile-hydrogens) are used. Such polymeric compositionshave "virtual crosslinks," i.e., crystalline aggregates that act likecrosslink sites, based on liquid crystal oligomers. The second type ofpolymeric composition is a crosslinked isocyanate-labile hydrogen basedlinkage based on a combination of a diisocyanate-labile hydrogen linearlinkage and preferably a component of triisocyanate or a tris-labilehydrogen or both. Both types of structures may also contain ionicfunctionality capable of forming thermally-reversible ionic bonds.

The thermally-reversible polymer compositions may also be considered ashaving three building blocks: 1) an isocyanate linking group, 2) a highperformance aromatic oligomer backbone group, and 3) a tougheningaliphatic prepolymer backbone group.

The isocyanate linking group includes the trifunctional isocyanatecrosslinker that is preferably reacted only with the aromatic oligomerbackbone group. Various balanced stoichiometry combinations of thesethree sequences can be combined to produce thermally-reversible polymercompositions that are crosslinked to a controlled extent with aromaticisocyanate-labile hydrogen linkages, or are not covalently crosslinked,but depend on "virtual" crystalline polymer crosslinks for highperformance.

Although phenolic hydroxyl is preferably used as the labile-hydrogenfunctionality, it is noted that other moieties also furnishlabile-hydrogen functionality. Such moieties include, but are notlimited to, aromatic amines or diamines, aromatic oximes and bis-, bi-,or dioximes, aromatic triazoles and bis- or ditriazoles, and aromaticimidazoles and imidazolines and bis- or diimidazoles and imidazolines.Less preferred are the aliphatic analogs of these compounds and primaryamines where excessive cross linking may be undesirable.

Polyisocyanate reactants used in this invention include aromatic,aliphatic, cycloaliphatic or aralkyl polyisocyanates containing fromabout 6 to 100 carbon atoms. When a linear composition is sought, thepolyisocyanate functionality should be about 2. The followingpolyisocyanates are expected to be useful: 1) aromatic isocyanates andprepolymers based on the following materials: 4,4'-diphenyl methanediisocyanate (MDI), 4,4',4"-triphenyl methane triisocyanate,1,4-phenylene, diisocyanate (DPDI), 1,3-phenylene diisocyanate, xylenediisocyanates such as 5,6-dimethyl1,3-phenylenediisocyanate and2,4-dimethyl-1,3-phenylenediisocyanate and other aromatic isocyanatesbased on other backbones such as naphthalene and 2) aliphaticisocyanates and prepolymers based on the following representativematerials: 1,3-cyclohexylene diisocyanate,4,4'-methylene-bis(cyclohexylisocyanate). A wide variety ofpolyisocyanates are known in the art as shown in, for example, U.S. Pat.No. 4,608,418 to Czerwinski et al., which is hereby incorporated hereinby reference.

The high-performance oligomer backbone group includes, but is notlimited to, polycarbonates, aromatic polyesters, polyimides,polyarylimidazolidines (including polyparabanic acids), andpolyarylenesulfides with phenolic hydroxyl or other labile-hydrogenend-group functionalities. Generally a labile-hydrogen functionality ofabout two is preferred.

The polycarbonates can be prepared from bisphenol A and phosgene in asuitable organic solvent using a controlled excess of bisphenol A toproduce phenolic hydroxyl end groups. Suitable polycarbonates includethose based on or containing in addition to bisphenol A, bisphenol F,4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylsulfone, hydroquinone,resorcinol, phenolphthalein or 4,4'-biphenol.

Aromatic polyester oligomers are based, for example, on 4- and 3-hydroxybenzoic acid, hydroquinone, resorcinol, 4,4'-biphenol,terephthalic acid, isophthalic acid and the 1,5-disubstitutednaphthalenes, in which both groups are either hydroxyl or carboxyl, orone is hydroxyl and the other is carboxyl. The phenol (aromatichydroxyl) groups are present in the reaction mixture, for example, amelt, predominantly in the form of the acetate ester obtained byreaction with acetic anhydride. Generally about half of the oligomerwill contain 4-hydroxybenzoic acid derived moieties. The remainder canbe derived from any of the other monomers, so long as the reactionmixture composition is such that the acetoxy and hydroxy to carboxylicacid group ratio will result in a hydroxyterminated oligomer with adegree of polymerization in the range of 1-20 and more preferably in therange of 1-10. Further the monomer mixture must be selected so that theoligomer will be obtainable as a melt under an inert atmosphere such asnitrogen or argon at temperatures that can be varied between about 200°C. and an upper temperature at which essentially no thermal degradationoccurs, i.e., about 300° C. or above.

Illustrative of the polyimides are those based on pyromelliticdianhydride (PMDA) and other commercially available aromaticdianhydrides and aromatic diamines such as p-phenylenediamine,4,4'-diaminodiphenylether and benzidine. Additional, nonpara-substituteddiamines such as m-phenylenediamine and 3,3'-diaminodiphenylether mayalso be used to lower the melting point of the oligomer.

Polyarylimidazolidines containing imidazolidine moieties such as4-imino-1,3-imidazolidine-2,5-dione-1,3-diyl;5-imino-l,3-imidazolidine-2,4-dione-I,3-diyl;1,3-imidazolidine-2,4,5-trione-l,3-diyl; and mixtures thereof and theirpreparation are described in U.S. Pat. Nos. 3,591,562 and 3,933,758 toPatton which are hereby incorporated herein by reference. Isocyanatesbased on p-phenylenediisocyanate, MDI, and the other isocyanates listedabove and in the Patton patents are reacted with hydrogen cyanideincluding hydrogen cyanide providers such as acetone cyanohydrin, usinga suitable catalyst such as an alkali metal cyanide and a tertiary aminesuch as triethylamine and an excess of isocyanate to provide first stageisocyanate-terminated oligomers of a controlled degree of polymerization(DP). The isocyanate terminated oligomer can then be blocked with phenolor reacted with any of a number of phenolic hydroxyl terminatedoligomers.

To avoid undue cross-linking between the imino hydrogen and isocyanatewith resultant gel formation, it has been found desirable to initiallyuse an excess of hydrogen cyanide to isocyanate. After the initialexothermic reaction begins to cool, a stoichiometric amount of isocyantesufficient to react with the excess of hydrogen cyanide and one hydroxylgroup of a dihydroxyl end capping group is added to the reactionfollowed immediately by the addition of the dihydroxyl end cappinggroup. The iminoimidazolidinedione ring(s) in the blocked or reactedoligomer can be hydrolyzed under appropriate conditions with a properly,water-diluted, mineral acid such as sulfuric acid or hydrochloric acidto provide the parabanic acid ring oxygen, i.e.,1,3-imidazolidine-2,4,5-trione, and the ammonium salt of the mineralacid. Generally the polyarylimidazolidines have a degree ofpolymerization (DP) of about one to about twenty with a lower DP ofabout three to ten and especially of about four preferred for betterproduct melt processability.

Illustrative polyarylsulfide oligomers suitable for the practice of thisinvention can be prepared by the condensation of dihaloaryl compoundswith sodium sulfide. Labile-hydrogen functionality such as found inhalophenolic compounds are used to control the molecular weight of theoligomer and to provide hydroxyl (labilehydrogen) end capping groups.Sodium sulfide nonahydrate is preferred to sodium sulfide since thelatter is unstable and can explode upon percussion or rapid heating. Bygenerating the sodium sulfide in situ and driving off the waters ofhydration, the reaction can be safely conducted in an open system, andthe reaction progress followed by monitoring the volatile byproducts.

Examples of useful polyarylsulfides include those containing any C₆ -C₁₄group such as, but not limited to, biphenyl, phenyl ether, anthracene,or anthraquinone and may contain pendant hydroxyl functionality Biphenylbackbone groups are preferred, not only because they may be readilyincorporated synthetically, but because even low molecular weightpara-hydrocarbon disubstituted biphenyl compounds show liquid crystalproperties. Polyarylsulfides that exhibit liquid crystalline behaviorare preferred, since they possess better melt-processing characteristics(lower viscosity and high shear thinning) relative to comparablenon-liquid crystalline materials.

Both lower cost dichloro- and higher reactivity dibromoaryl compoundscan be used. Representative examples of haloaryl compounds include4,4'-dibromobiphenyl; 1,5-dichloroanthraquinone; 4-bromophenyl ether;9,10-dibromoanthracene; 2,4 dibromophenol while 4-bromochlorophenol canserve as halophenolic end cappers. Non-aqueous solvents capable ofdissolving the product are used with the preferred reaction solventbeing 1-methyl-2-pyrrolidinone due to its solvency strength, relativelyhigh boiling point and miscibility with product precipitation media suchas water, methanol or mixtures thereof.

Toughening prepolymers provide ambient or low temperature flexibilityand toughness to the final polymer composition. A wide variety offlexible prepolymer materials may be used including polycaprolactonediols such as Union Carbide PCP, polytetramethylene ether glycols suchas DuPont Teracol and polyaliphatic carbonate diols such as PPGDuracarb. Other toughening prepolymers include hydroxy-ended aliphaticpolyesters such as adipic acid or sebacic acid polyesters withα,ω,-butane, pentane or hexane diols, saturated phthalic acid-basedpolyesters (long, or non-drying alkyds) with any of the simple diols andsimple polyether glycols such as polypropylene glycols.

Additives as are commonly added to polyurethane products such asantioxidants, UV stabilizers, colorants, fillers, etc., can be added tothe polymer composition of the present invention in conventionalamounts.

The polymer composition of this invention can be coated onto a suitablesubstrate by applying such composition to the substrate and then heatingthe covered substrate to a temperature sufficient to form a bond.Operative methods for covering a surface include powder coating andapplying a film to the substrate. In powder coating, the composition isground into a powder with particle sizes less than about 250 microns andapplied to a substrate either by electrostatic spray or by fluidizedbed. The covered substrate then can be baked at a temperature sufficientto form a uniform fused coating bonded to the substrate. In anothermethod, a film of the polymer material can be placed on the substrateand then baked. Alternatively, the thermally reversible material can beapplied to a heated substrate such that bonding occurs as the materialis applied to the substrate. When used as a hot melt adhesive, thepolymer composition can be applied between two substrates and the twosubstrates heated to form a bond. Alternatively the polymer compositioncan be applied to at least one heated substrate followed by pressing thesecond substrate to the first. When thermal conductivity is not asignificant factor, the heated polymer components can be applied withoutsubstrate heating.

The following examples are disclosed to further teach the practice ofthe invention and are not intended to limit the invention as it isdelineated in the claims.

EXAMPLE A Preparation of Bis-Hydroquinone Ester of Isophthalic Acid

In order to provide an additional quantity of oligomer, a 1.5 foldlarger scale production of the bishydroquinone ester of isophthalic acidwas undertaken. The experimental apparatus and details were essentiallyidentical to those described in EXAMPLE 5 of our previous application,U.S. application Ser. No. 07/651,020, Markle et al, filed on 02/04/92,now U.S. Pat. No. 5,097,010 the disclosure of which is herebyincorporated by reference.

Three hundred seventy-five milliliters of dry (H₂ O<0.001%)dimethylacetamide (DMAC; Aldrich 21,707-2) and 65.3 g dry (over CaH₂)pyridine (Aldrich 36,057-0; 66.7 cc.; 0.825 moles) were added to ahot-air gun dried 3 l, 3 neck round bottom flask equipped with astoppered pressure equalizing addition funnel, Trubore stirrer (Teflonpaddle), inert gas (argon) inlet and outlet, heating mantle with I² RThermowatch controller, and external thermocouple monitor thermometer tomeasure pot temperature. While stirring slowly with an argon flush,hydroquinone (HQ; 99%; Aldrich 1,790-2; 327.0 g; 3.0 moles) was addedover a 5 minute period. The mixture was then heated to ˜50° C. where allthe hydroquinone dissolved. A solution of isophthaloyl chloride (IPC;Aldrich 36,0570-0 74.6 g; 0.375 moles) in 450 ml additional drydimethylacetamide was prepared in a 1-liter erlenmeyer flask. Gentleheating was required to completely dissolve the isophthaloyldichloride.The solution was transferred to the 1-liter dropping funnel and addeddropwise (˜5 drops/second) to the rapidly stirred (50° C.) HQ solutionover a 1.5 hour period. The reaction mixture was then slowly heated to˜82° C. where the pyridine appeared to reflux. After an additional 2hours, the heating mantle was turned off and the solution allowed tocool overnight under an argon flush prior to precipitation. The reactionmixture was precipitated by slowly pouring the solution into 15 ldistilled water in a 5 gallon pail equipped with a Talboy stirrer andstainless steel dual blade Jiffy mixer. The white suspension was stirredfor an additional 30 minutes, then allowed to settle (digest) for ˜2hours. The precipitate was then filtered with a Buchner funnel and no. 4Whatman filter paper, and washed with an additional 1800 ml distilledwater. A solubility check of the product showed it to be soluble inmethanol, ethanol, and isopropanol, and insoluble in methylene chlorideand toluene. The product was transferred to an evaporating dish, driedovernight in a vacuum oven (˜30 in Hg vacuum, 65° C.), then ground witha mortar and pestle, returned to the vacuum oven for another day (<0.5wt % loss) and placed in a jar. The final washed, dried, ground productyield was 103.9 g or 79.1 percent recovery (identical to the smallerscale batch-EXAMPLE 5 in our previous application) based on 131.4 gtheoretical yield of the bis-hydroquinone ester of isophthalic acid. DSCthermal analysis showed a melting exotherm at 215° C. Opticalmicroscopic analysis using polarized light showed an initial meltingpoint of 211° C., a liquid-crystalline region between 211° and 219° C.illustrated in FIG. 1 and a complete melt occurring at 223° C.

EXAMPLE B Preparation of Phenolic-Hydroxyl Terminated BisphenolA/Phosgene Polycarbonate Oligomers

In order to provide an additional quantity of oligomer for hot meltadhesive formulation, a 4.5 fold larger-scale preparation of thephenolic-hydroxyl terminated bisphenol A/phosgene polycarbonate oligomerwas undertaken. The experimental apparatus and details were essentiallyequivalent to those described in EXAMPLE 6 of our previous application,U.S. application Ser. No. 07/651,020, Markle et al, filed on 02/04/91,the disclosure of which is hereby incorporated by reference. The 10×flask volume scale-up (300 ml to 3 l) allowed a doubling of the solvent(methylene chloride) used which provided better mixing and heattransfer. The following was added to a 3 liter, 3 neck round bottomflask equipped with a Trubore stirrer (Teflon paddle), inert gas (argon)inlet and outlet with flowmeter: 4,4'-Isopropylidenediphenol (bisphenolA, Aldrich 13, 302-7, 99.4%, 204.23 g, 0.90 moles); Triethylamine(Aldrich 13,206-3; dried oven CaH₂ ; 234.5 ml, 1.70 moles); andMethylene chloride (CH₂ Cl₂ ; Burdick and Jackson 300-4, dried oven CaH₂; 1350 ml). The flask was surrounded by a water/ice bath to control pottemperature.

The Phosgene solution (Fluka 79380, 20% in toluene; 1.93 Molar, 2% HClimpurity, 365.14 g, 0.810 moles) was added dropwise (˜5 drops/second)over a one hour period, using an ice bath to maintain the pottemperature at 23±1° C. Precipitate was noted after about 55.5% of thesolution had been added. The reaction mixture was stirred for anadditional 2.5 hours at which point it appeared to be more viscous. Thereaction mixture was allowed to stand overnight under an argon purge.The reaction mixture was then filtered and the precipitate washed withCH₂ Cl₂ and dried in a vacuum oven. A total of 138.0 g of by-producttriethylamine hydrochloride (or ˜62.3% theoretical) was recovered. Themissing salt was presumed dissolved in the oligomer solution.

The polycarbonate oligomer solution was concentrated down to ˜1 l andprecipitated in a ten fold excess (˜10 l) of reagent grade methanol in a5 gallon pail equipped with a Talboy stirrer and stainless steeltwin-rotor Jiffy mixer. The precipitate was allowed to settle and wasthen filtered through a Buchner funnel with No. 2 Whatman filter paperand washed with ˜1 l additional methanol. The product was thentransferred to an evaporating dish and dried overnight (30 in Hg.vacuum; 65° C.). The final polycarbonate product yield was 142.57 g(63.1% theoretical). DSC thermal analysis showed a melting exotherm at182° C.

EXAMPLE C Hot Melt Polycarbonate Composition I

The polycaprolactone diol (PCP-530; Aldrich 18,940-5; 3.280 g),paraphenylphenol (PPP; Aldrich 13,434, 97%; 0.0180 g), bis-hydroquinoneisophthalic acid diester oligomer (HQ/IPA/HQ, phenol end groups fromExample A; 1.696 g) and polycarbonate (PC; from Example B; 0.580 g) weremelted together while hand mixing with a stainless steel spatula in a180 ml electrolytic (deep) beaker under an inert gas (argon) blanket atabout 210° C. Trimethyolpropane (TPM, 0.101 g) with a hydroxy equivalentweight of 44.7 was reacted in situ with 4,4'diphenylmethane diisocyanate(crystalline MDI, Isonate 125M, Dow, mp 37° C.; 3.116 g) with a hydroxyequivalent weight of 44.7 to give an aromatic triisocyante that wasadded to the previous melt while the melt was stirred at ˜150° C. It wasquickly incorporated in the melt and the viscosity increased to a fairlyhigh level in about five minutes. The melt was heated to 180° C. and theviscosity decreased to a very easily stirred level. Adhesive specimenswere then hand assembled by applying melted adhesive to 0.5×1.0 inchareas (1.27×2.54 cm) on the ends of 1×3×0.032 inch (2.54×7.62×0.0813 cm)dull finish steel 1/4 hard (R-13) coupons (Q Panel Inc., Cleveland,Ohio). The steel test coupons had been hand cleaned/degreased first witha Kimwipe soaked with toluene, then one soaked with methyl alcohol, andpreheated on a hot plate set at ˜180° C. surface temperature. The testsamples were adjusted to give 0.5 in² (1.61 cm²) contact area, firmlypressed together by hand, the excess adhesive exudate scraped away andthe assembled test specimen clamped together with two, one-half inch,spring loaded, IDL binder clips. One clip was placed on each side of theoverlapped bond area. The partially cooled samples were then placed in a200° C. air oven briefly (3-5 minutes) to insure that the adhesive hadflowed and contacted all the metal surfaces. The samples were thenallowed to cool to ambient temperature and placed in a constanttemperature/humidity (73 F, 20% relative humidity) room to condition for24 hours prior to testing.

EXAMPLE D In-Mold Coatings to Produce Class "A" Finish on StampableThermoplastic Sheet Composites

When thermoplastic sheet composite parts are formed in a mold, thedifferential changes in dimension between the glass fiber or otherreinforcement and polymer causes surface roughness that is not of class"A" finish surface quality, that is, suitable for exterior finishapplications such as automotive finishes. By adding a coating just afterpart formation, that material can replicate the smooth mold surface andfill in the depressions in the composite. To do this, the coatings mustbe of low viscosity, have good adhesion to the composite, and notsolidify in an uneven manner. Composition I has these characteristics.The two polymers of interest in thermoplastic sheet composites arepolypropylene (PP) and polyethylene terephthalate (PET). Both are poorlyadhered to by most coatings. Therefore, conventional in-mold coatingsused to provide a class "A" finish to other composites, such as thosebased on sheet molding compound cannot be used with polypropylene andpolyethylene terephthalate composites. Composition I was found to adheretightly to both of these materials fulfilling one of the primaryrequirements for the in-mold coating. No other material is known to dothis to our knowledge. The polymer also has a low viscosity meaning itwill flow easily to provide good coverage over the molded part.

The tight, in-mold bond on the polypropylene andpolyethylene-terephthalate composites with composition I was obtained at350° F. and 600-800 psi pressure. Temperature higher than 400° F.resulted in irregular coated surfaces. A thin, 406 mil thick coating wasproduced on the composites providing both a tightly-adhering, and highgloss finish.

A 5-mil thick Kapton (DuPont polyimide) sheet between composition I andthe smooth mold surface permitted the composite to release from themold. Attempts to use thin teflon sheets as release agents resulted indull, irregular coatings.

To test the adhesion of the composition I to the polypropylenecomposite, tensile lap shear specimens were prepared by sandwichingcomposition I between two layers of polypropylene glass-filled compositewith a 1"×1"overlap. Test results are given in Table 1.

EXAMPLE E Preparation of Phenolic-Hydroxyl Terminated BiphenylenesulfideOligomers

The following were added to a 3 liter, 3 neck round bottom flaskequipped with a Trubore stirrer (Teflon paddle), inert gas (argon) inletand outlet with flowmeter, Claisen head with both pot and distillatethermometers, water cooled distillation condenser, distillationtake-off, and receiver flask: 91.74 g 4,4'Dibromobiphenyl (4,4'DBBP;Aldrich 92-86-4; 98%, 0.30 moles); 26.21 g 4-Bromophenol (4-Bp; Aldrich106-41-2; 99%; 0.15 moles); 90.07 g Sodium Sulfide Nonahydrate (Na₂S.9H₂ O; Aldrich 1313-84-4; 0.375 moles); 39.75 g Sodium carbonate (Na₂CO₃ ; Baker 3602-01; 0.375 moles); and 1.8 l 1-methyl-2-pyrrolidinone(NMP; Aldrich 27,045-8, 99+%). The flask was surrounded by a 2-pieceGlasscol spherical heating mantle with internal thermocouple leads tomeasure flask surface temperature, connected to independent Variacrheostats, controlled by an I² R Thermowatch temperature L8-2000 SScapacitance monitor attached to the pot thermometer.

The Aquamarine blue mixture was stirred under a slow Argon purge(0.3-0.4 SCFH) while heating (˜40/˜55 V; Top/Bottom) to the targetpolymerization temperature of ˜165° C. As the pot temperature rose over˜108° C., condensate was noted so the Claisen adapter was insulated withglass wool, the Argon flow rate increased to ˜1.0 SCFH, and thedistillate (water from Na₂ S.9H₂ O) collected. The temperature wasmaintained at ˜165° C. for 2.5 hours during which time the distillatecollection rate slowed and vapor temperature dropped. The heatingmantles were then removed and the flask was cooled with an air line tonear room temperature. The resulting dark emerald green solution wasslowly added to rapidly stirring 14 l of Water/methanol (71/29, V/V) ina 5 gallon pail equipped with a Trubore stirrer and stainless steeltwin-rotor Jiffy mixer. The beige precipitate/suspension was stirred for˜30 minutes, then allowed to settle overnight.

The product was recovered by filtration using a Buchner funnel and no. 4Whatman filter paper, initially dried, then placed in a 25-50 μ glassbutted funnel and washed with ˜500 ml methanol. The washed product wasthen placed in a vacuum oven (˜30 in Hg, 65° C.) dried, ground with amortar and pestle, returned for further drying and placed in a screw-capamber bottle. The final washed, dry, ground product yield was 60.85 g or˜79.6 percent of the theoretical yield of 76.45 g for the DP=4 oligomer(MW=955.3 g/mole theoretical).

Samples of the product were analyzed using Differential ScanningCalorimetry (DSC), Infrared Spectroscopy (ATR) and optical microscopictechniques. The DSC showed a single sharp peak near ˜153° C., indicatinga relatively pure compound. The infrared analysis showed the presence ofhydroxyl end-group functionality. The optical microscopy (usingpolarized light) as a function of temperature indicated that thematerial possessed strong liquid-crystalline behavior as shown in FIG. 2over a broad range, from ˜175° C. to over ˜220° C, completely melting at˜242° C. The presence of reactive hydroxyl end-group functionality wasconfirmed by reaction of the product with a stoichiometric amount of MDIproducing a thick urethane polymer.

Hot melt adhesive test samples were prepared as described previouslyunder EXAMPLE C, Hot Melt Polycarbonate Composition I, but with thephenolic-hydroxyl terminated biphenylenesulfide oligomer beingsubstituted for the polycarbonate portion on an equivalent basis. Lapshear strength results were obtained and preliminary indicated thematerial to have a lap shear strength of about two times that ofcommercial polyester PE 6300 from H. B. Fuller.

EXAMPLE F Preparation of Poly 4(or 5)-imino-1,3-imidazolidine-2,5(or4)-dione-1,3-diyl Oligomers with Phenolic Hydroxyl End Groups

A 500-ml three-neck flask was fitted with a Trubore stirrer with Teflonblade (driven by a T-line laboratory electrical stirrer), an argon gasinlet and a thermometer positioned to penetrate into the reactionsolution via an adapter with a gas outlet side arm. The flask was flamedried and cooled under an argon flush. Then 31.7 g (0.127 mole) of MDI(Dow Isonate 125 M) and 150 ml NMP (Aldrich 27,045-8, 99+ percent, driedover Fluka 3A type molecular sieve 69828) were placed in the flask. TheNMP was heated until the MDI all just dissolved, then cooled to nearambient. Then 8.896 g acetone cyanohydrin (Aldrich A1,000-0 dried oversame Fluka molecular sieve) were added by syringe. The 1.0 cc oftriethylamine (TEA; Aldrich 13,206-3 dried over the Fluka molecularsieves) was added by syringe, followed by 2.5 cc of a solution of NaCN(0.2000 g/100 ml NMP, same NMP as above). Immediately an exotherm wasnoted. The temperature of the well stirred solution rose from 28° C. to43.8° C. over the next 1 hr 17 mins. The reaction flask was insulatedwith Pyrex wool during this period. The temperature then began to drop.After about 15 mins, it was 43.0° C. Then 4.65 g (0.0422 mole) ofAldrich H1,790-2 hydroquinone, 99 percent was added and dissolved in 25ml of the same dry NMP. It was added all at once. The temperatureimmediately began to rise again. In 7 mins, it had reached 47.0° C. Atthis point, the viscosity increased very rapidly and the initiallymoderately viscous, clear light yellow solution gelled to a very stiffgel which could not be stirred. The gel was left to stand overnightunder the Ar flush. The next morning the gel had completely disappeared.The mixture had spontaneously reverted to a clear easily stirredmoderate viscosity liquid. A small sample of this solution whenprecipitated in methanol, washed with methanol and dried, melted to aclear moderate viscosity liquid at 270°-295° C. Apparently acrosslinking reaction of terminal isocyanate groups with pendant imino(═NH) sites produced a branched oligomer which crosslinked when chainextended with the hydroquinone. However, unreacted hydroquinone hydroxylgroups then may have displaced these crosslinking urea linkages to formmore stable urethane bonds. Hence the final product may have assumed thenearly linear oligomer structure that the 6/5 MDI/HCN mole ratio waschosen to provide. The end groups are presumed to be p-hydroxyphenylgroups from end- capping of the terminal isocyanates with hydroquinone.This is a unique, difunctional phenolic end-group oligomer.

EXAMPLE G Preparation of Polyparabanic Acid Oligomer With PhenolicHydroxyl End Groups

A similar reaction to Example F was carried out using the same reagentsand apparatus. However, an excess of the HCN provider (acetonecyanohydrin) was used in a first stage reaction. Hence 8.511 g (0.1000mole) of acetone cyanohydrin were added to a solution of 12.151 g(0.0485 mole) MDI in 150 cc NMP. To this were added 0.5 cc of the dryTEA, followed by 2.0 ml of the 0.2000 g/100 ml solution of NaCN in NMP.An immediate exotherm was noted. In 15 mins the temperature had climbedfrom 28° C. to 53.5° C. It then started to fall and reached 47° C. afteranother 10 mins. Then 25.026 g (0.1000 mole) MDI in 100 cc warm NMP and11.011 g (0.0500 mole) hydroquinone in 50 cc warm NMP were addedseparately, the MDI first all at once, followed by the HQ, all at once,about 2 mins later. Another exotherm occurred with the temperaturerising to 58° C. in about 10 mins. The yellow clear solution increasedin viscosity initially, then fell again to a moderate level. No gelformation was noted. The mixture was stirred overnight under argon at amoderate rate while maintaining the temperature at 45° C. The productsolution was perhaps slightly less viscous but otherwise unchanged. Itwas precipitated in ˜3 liters of methanol in a Waring blender run atmoderate speed and filtered on a coarse (˜25 μm) fritted funnel. It waswashed seven times in the blender with about 600 ml portions ofmethanol, until the methanol wash demonstrated no turbidity when droppedinto tap water. A small portion was dried (0.7 g) and the melting pointof the imino-group containing oligomer measured on the Fisher Johnsmelting point hot stage. It melted at 240°-250° C.

The remainder of the oligomer was redissolved in about 350 ml of NMP inthe blender. Then 11 g of concentrated HCl, diluted with an equal volumeof distilled water, was added to the rapidly stirred yellow, clearsolution. Copious precipitation of NH₄ Cl occurred immediately and thesolution became a clear, green color. The amount of HCl used wasslightly in excess of the amount theoretically required (˜9.8 g) toconvert the C═NH groups to --C═O groups, white providing NH₄ Clby-product. The clear supernatant was then precipitated in distilledwater and filtered through the 25 μm frit. The white powder was washedthree times with water, three times with methanol and three times with30°-60° C. pet ether and air dried. The slightly yellowish-white powdermelted (Fisher Johns) at 220°-230° C. DSC analysis indicated a meltingpoint of ˜207° C. Hot melt adhesive test samples were prepared asdescribed under EXAMPLE C, Hot Melt Polycarbonate Composition I, butwith the polyparabanic acid oligomer with phenolic hydroxyl end groupsbeing substituted for the polycarbonate portion on an equivalent basis.Lap shear strength results were obtained and preliminary resultsindicated the material to be comparable to commercial polyesteradhesives such as PE 6300.

While there has been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,intended to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

                  TABLE 1                                                         ______________________________________                                        LAP SHEAR STRENGTH OF COMPOSITION I                                           AND COMMERICAL (PE 6300) HOT MELT                                             ADHESIVES WITH POLYPROPYLENE SUBSTRATES                                       (Adhesive Area 1" × 1" = 1 sq in.)                                                         Lap Shear Strength, psi                                    Adhesive  Trial  Load, lbs         avg  rounded                               ______________________________________                                        Composition I                                                                           a      Broke in grips    59.8 (60)                                            b      53          53                                                         c      83.5        83.5                                                       d      Broke in grips                                                         e      43          43                                               PE 6300   a      118         118   73.7 (74)                                            b      61          61                                                         c      42          42                                               ______________________________________                                    

We claim:
 1. A process for preparing a polyarylimidazolidine oligomerwith about one to about twenty arylimidazolidine repeat units and havingphenolic hydroxyl end groups, said process comprising:a. mixing anexcess of hydrogen cyanide with an aryl diisocyanate and a catalyst inan anhydrous solvent to afford an exothermic reaction; b. adding astoichiometric amount of said aryl diisocyanate to react with saidexcess hydrogen cyanide and one hydroxyl of a phenolic dihydroxyl endcapping group after the exothermic reaction has cooled slightly; and c.adding immediately thereafter said dihydroxyl end capping group.
 2. Theprocess for preparing the polyarylimidazolidine oligomer of claim 1further comprising the step of treating the product from step c with amineral acid to convert an imino group to a carbonyl group.
 3. Apolyarylimidazolidine oligomer consisting of of about one to abouttwenty arylimidazolidine repeat units and phenolic hydroxyl end groups.4. The polyarylimidazolidine oligomer of claim 3 having a degree ofpolymerization of about three to about ten.
 5. The polyarylimidazolidineoligomer of claim 4 having a degree of polymerization of about four.